1. Field of the Invention
The present invention relates generally to folders of printing presses and more particularly to a device and method for folding a signature of printed material.
2. Background Information
Web printing presses print a continuous web of material, such as paper. The continuous web is then processed in a folder of the printing press. Folders can provide for particular desired folds in a finished printed product. A cutting unit is typically included to cut the web into individual signatures. Folds often need to be provided both to the web and the signatures which are cut from the web.
U.S. Pat. No. 5,030,193 purports to disclose a folder apparatus which includes a first folder assembly which forms a first fold in a web of sheet material along the path of movement of the sheet material. This first fold is performed by pulling the web over a triangular-shaped stationary folder board and feeding the web through a pair of nip rollers to set the fold. The web is then cut by a cutting cylinder to form signatures, the signatures then being carried by a tucking cylinder to a jaw cylinder. A tucking blade of the tucking cylinder pushed the signature into a set of jaws of the jaw cylinder to create the second fold, which is transverse to the first fold. The signatures are then sent to a third folder assembly having an array of tapes which grip the signatures and move them through the third folder assembly. The array of tapes maintain a straight direction within the third folder assembly. However, two stationary formers at the sides of the tapes accept the sides of the signature as the signature enters the third folder assembly. These formers then converge at an angle to the tapes, so as to force the outer edge portions of the signature upwardly, thereby forming the fold of the third folder assembly.
The first folder assembly of the above-cited patent has the disadvantage that it is difficult or impossible to be used to fold signatures, a web must be pulled over the former board. The second folder assembly has the disadvantage that many moving parts are required. The third folder assembly has the disadvantage that the design is complicated and requires a large number of belts of different length.
In addition, known chopper folding mechanisms often require more than one chopper folder mechanism to support a single printing press running at fall speed. The signature stream thus often must be split and decelerated, which requires auxiliary devices such as diverters, slow down sections and integrators. These auxiliary devices increase the risk of fold inaccuracies, as the signatures must interact with each device and still maintain proper position.
An object of the present invention is to provide for a device and method for folding signatures whereby damage to the printed products may be reduced. An additional or alternative object of the present invention is to provide for a simplified device for folding signatures.
The present invention provides a signature folding device including a first transport device for transporting a first part of a signature, and a second transport device next to the first transport device for transporting a second part of the signature, the second transport device being skewed with respect to the first transport device so as to move the second part of the signature toward the first part of the signature.
Preferably, the first and second transport devices include belts which grip the respective parts of the signature from above and below.
Since the second transport device skews toward the first transport device, the signature between the first part and the second part rises to begin to form a fold.
The folding device may further include a fold guide into which the signature may enter after exiting the first and second transport devices. After exiting the fold guide the folded signature may be carried by a plurality of vertical transport belts.
The folding device also preferably includes vertical nip belts to receive the fold and to aid in setting the fold. The second transport device may include a skewed belt section followed by a straight belt section, the straight belt section preferably being located before a fold guide.
The skewed belt section preferably runs at a slightly higher speed than the first transport device. The first part and the second part of the signature thus can travel in a same direction at the same speed, even while the fold is being created.
The present invention also provides a method for folding a signature including the steps of transporting a first part of the signature in a first direction, and transporting a second part of the signature in a second direction, the second direction being skewed toward the first direction so that a fold begins to form in the signature.
The method further may provide moving the fold into a pair of vertical nip belts. The method also may provide that the signature is moved into a fold guide after the transporting steps.
Preferably, the transporting of the second part occurs at a speed slightly greater than the transporting of the first part.
The transporting steps preferably are accomplished by having belts grip the respective parts of the signature from above and below.
The present invention provides a simplified device and method for folding a signature. The moving parts of the device may be simple belt drives. No complicated mechanisms are required.
Because the fold takes place while both halves of the signature are held securely by the first and second transport devices, it is possible to accomplish accurate high speed folding and to eliminate the need for a chopper mechanism.